David Partridge

Outpatient parenteral antibiotic therapy for infective endocarditis: a review of 4 years' experience at a UK centre

Objectives To review the role of outpatient parenteral antibiotic therapy (OPAT) in the management of infective endocarditis (IE) with the aim to guide further development of the service modality both locally and at other centres, in light of the evolving recommendations on patient suitability in international guidelines. Methods A retrospective case review of all patients receiving OPAT for IE in Sheffield between January 2006 and October 2010 was conducted. Data were collected on site and microbiology of infection, antibiotic regimens, adverse events during OPAT therapy and outcomes were studied. Results A total of 36 episodes of IE were treated in 34 patients. All patients received initial treatment as inpatients. Treatment was successful in 34/36 episodes (94.4%) with no evidence of recurrence at a median of 30 months follow-up. One patient had a relapse 2 months after completion of OPAT for enterococcal endocarditis and was found to have concurrent chronic prostatitis. One patient died of a ruptured pulmonary root abscess while receiving OPAT. Adverse events occurred in 12 episodes (33.3%), of which seven were line associated. In four cases adverse events resulted in re-hospitalisation. A successful outcome was achieved in 22/24 episodes (91.7%) deemed to be less suitable for OPAT due to higher risk of complications by Infectious Diseases Society of America guidelines. Conclusions OPAT is a safe and effective means of completing therapy for IE, including prosthetic valve endocarditis and other cases at a higher risk of complicated disease. However, the relatively high rate of adverse events highlights the need for well-developed protocols and policies for patient selection and follow-up within the context of a formal OPAT service.

Prosthetic valve endocarditis caused by Pseudomonas mosselii

We describe a case of Pseudomonas mosselii prosthetic valve endocarditis that was successfully treated with antibiotic therapy in the absence of valve replacement. P. mosselii is a highly unusual cause of endocarditis and there are few case reports of curative treatment of pseudomonal prosthetic valve endocarditis with antibiotics alone.

Evaluation of an agar-gradient minimum-inhibitory-concentration method (the Etest) as a rapid and direct measure of antimicrobial susceptibility in Gram-negative bacteraemia

BACKGROUND The selection of appropriate antibiotics to treat Gram-negative bacteraemia may be life-saving. Rapid methods of antimicrobial susceptibility testing have sought to guide early antibiotic selection and usage. We sought to evaluate whether a combination of chromogenic agar and six Etest gradient diffusion strips could be used to provide a clinically useful, direct rapid antimicrobial susceptibility test result following 4 hours of incubation.

Letter to the Editor: Aseptic Loosening of Total Hip Arthroplasty: Infection Always Should be Ruled Out

We welcome the study by Parvizi et al. [3] published in the May edition of the journal and the attention it draws to the misdiagnosis of aseptic loosening which may occur if infection is not rigorously excluded. This supports the work of other authors, who have confirmed infection in as much as 13% of cases of presumed aseptic loosening [2]. The methodology of the study however poses some questions. First, the distinction between patients with infection and without infection must be questioned as a large proportion of patients deemed to be correctly diagnosed as having aseptic loosening did not have specimens sent for culture. In patients who did have specimens sent, a minimum of three intraoperative specimens were cultured but this number has been shown to be inadequate [1]. Sending less than five intraoperative specimens is especially likely to be insensitive for the low virulence organisms which are most likely to masquerade as aseptic loosening. There is also the likelihood that a proportion of the patients assigned to Group 1 (prosthetic joint infection) on the grounds of definite prosthetic joint infection at the time of subsequent rerevision actually had infection after their revision surgery rather than representing falsely diagnosed aseptic loosening. Also, in patients assigned to Group 1 on the basis of positive cultures, the number of tissues required to be positive for a diagnosis of infection is not stated. It is recognized that positive cultures from one tissue specimen are likely to represent contamination, again emphasizing the need to send an adequate number of specimens [1]. After arrival at the laboratory, the microbiologic processing of the specimens is not detailed. Variations in processing technique are recognized to greatly impact on the sensitivity and specificity of orthopaedic tissue culture. Correctly diagnosing prosthetic joint infection is a team effort requiring an appropriate number of correctly taken specimens to be rapidly transported to a microbiology laboratory. The specimens need to be processed correctly, avoiding contamination but optimizing the potential for growth of any pathogenic organisms. Important in this regard are the use of broth cultures (and their subsequent terminal subculture at the end of prolonged incubation) in addition to direct cultures and prolongation of incubation to detect slow-growing low virulence organisms [4]. Finally, the organisms grown need to be identified correctly, their significance interpreted, and an appropriate management plan formulated between surgeon and microbiologist. Ideally patients with possible prosthetic joint infections should be under the care of a surgeon with a specialist interest in the field and the diagnostic process facilitated by the use of a microbiology laboratory and reporting microbiologist specializing in orthopaedic infections. By adopting this approach the number of incorrect diagnoses of aseptic loosening can be minimized.